/* atof_ieee.c - turn a Flonum into an IEEE floating point number
   Copyright (C) 1987, 1992 Free Software Foundation, Inc.

   This file is part of GAS, the GNU Assembler.

   GAS is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   GAS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GAS; see the file COPYING.  If not, write to
   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "as.h"

extern FLONUM_TYPE generic_floating_point_number;	/* Flonums returned here. */

#ifndef NULL
#define NULL (0)
#endif

extern const char EXP_CHARS[];
/* Precision in LittleNums. */
#define MAX_PRECISION (6)
#define F_PRECISION (2)
#define D_PRECISION (4)
#define X_PRECISION (6)
#define P_PRECISION (6)

/* Length in LittleNums of guard bits. */
#define GUARD (2)

static const unsigned long mask[] =
{
  0x00000000,
  0x00000001,
  0x00000003,
  0x00000007,
  0x0000000f,
  0x0000001f,
  0x0000003f,
  0x0000007f,
  0x000000ff,
  0x000001ff,
  0x000003ff,
  0x000007ff,
  0x00000fff,
  0x00001fff,
  0x00003fff,
  0x00007fff,
  0x0000ffff,
  0x0001ffff,
  0x0003ffff,
  0x0007ffff,
  0x000fffff,
  0x001fffff,
  0x003fffff,
  0x007fffff,
  0x00ffffff,
  0x01ffffff,
  0x03ffffff,
  0x07ffffff,
  0x0fffffff,
  0x1fffffff,
  0x3fffffff,
  0x7fffffff,
  0xffffffff,
};


static int bits_left_in_littlenum;
static int littlenums_left;
static LITTLENUM_TYPE *littlenum_pointer;

static int
next_bits (number_of_bits)
     int number_of_bits;
{
  int return_value;

  if (!littlenums_left)
    return (0);
  if (number_of_bits >= bits_left_in_littlenum)
    {
      return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;
      number_of_bits -= bits_left_in_littlenum;
      return_value <<= number_of_bits;

      if (--littlenums_left)
	{
	  bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
	  --littlenum_pointer;
	  return_value |= (*littlenum_pointer >> bits_left_in_littlenum) & mask[number_of_bits];
	}
    }
  else
    {
      bits_left_in_littlenum -= number_of_bits;
      return_value = mask[number_of_bits] & (*littlenum_pointer >> bits_left_in_littlenum);
    }
  return (return_value);
}

/* Num had better be less than LITTLENUM_NUMBER_OF_BITS */
static void
unget_bits (num)
     int num;
{
  if (!littlenums_left)
    {
      ++littlenum_pointer;
      ++littlenums_left;
      bits_left_in_littlenum = num;
    }
  else if (bits_left_in_littlenum + num > LITTLENUM_NUMBER_OF_BITS)
    {
      bits_left_in_littlenum = num - (LITTLENUM_NUMBER_OF_BITS - bits_left_in_littlenum);
      ++littlenum_pointer;
      ++littlenums_left;
    }
  else
    bits_left_in_littlenum += num;
}

static void
make_invalid_floating_point_number (words)
     LITTLENUM_TYPE *words;
{
  as_bad ("cannot create floating-point number");
  words[0] = (LITTLENUM_TYPE) ((unsigned) -1) >> 1; /* Zero the leftmost bit */
  words[1] = (LITTLENUM_TYPE) -1;
  words[2] = (LITTLENUM_TYPE) -1;
  words[3] = (LITTLENUM_TYPE) -1;
  words[4] = (LITTLENUM_TYPE) -1;
  words[5] = (LITTLENUM_TYPE) -1;
}

/************************************************************************\
 *	Warning: this returns 16-bit LITTLENUMs. It is up to the caller	*
 *	to figure out any alignment problems and to conspire for the	*
 *	bytes/word to be emitted in the right order. Bigendians beware!	*
 *									*
\************************************************************************/

/* Note that atof-ieee always has X and P precisions enabled.  it is up
   to md_atof to filter them out if the target machine does not support
   them.  */

/* Returns pointer past text consumed. */
char *
atof_ieee (str, what_kind, words)
     char *str;			/* Text to convert to binary. */
     char what_kind;		/* 'd', 'f', 'g', 'h' */
     LITTLENUM_TYPE *words;	/* Build the binary here. */
{
  /* Extra bits for zeroed low-order bits.  The 1st MAX_PRECISION are
     zeroed, the last contain flonum bits. */
  static LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
  char *return_value;
  /* Number of 16-bit words in the format. */
  int precision;
  long exponent_bits;
  FLONUM_TYPE save_gen_flonum;

  /* We have to save the generic_floating_point_number because it
     contains storage allocation about the array of LITTLENUMs where
     the value is actually stored.  We will allocate our own array of
     littlenums below, but have to restore the global one on exit.  */
  save_gen_flonum = generic_floating_point_number;

  return_value = str;
  generic_floating_point_number.low = bits + MAX_PRECISION;
  generic_floating_point_number.high = NULL;
  generic_floating_point_number.leader = NULL;
  generic_floating_point_number.exponent = 0;
  generic_floating_point_number.sign = '\0';

  /* Use more LittleNums than seems necessary: the highest flonum may
     have 15 leading 0 bits, so could be useless. */

  memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION);

  switch (what_kind)
    {
    case 'f':
    case 'F':
    case 's':
    case 'S':
      precision = F_PRECISION;
      exponent_bits = 8;
      break;

    case 'd':
    case 'D':
    case 'r':
    case 'R':
      precision = D_PRECISION;
      exponent_bits = 11;
      break;

    case 'x':
    case 'X':
    case 'e':
    case 'E':
      precision = X_PRECISION;
      exponent_bits = 15;
      break;

    case 'p':
    case 'P':

      precision = P_PRECISION;
      exponent_bits = -1;
      break;

    default:
      make_invalid_floating_point_number (words);
      return (NULL);
    }

  generic_floating_point_number.high
    = generic_floating_point_number.low + precision - 1 + GUARD;

  if (atof_generic (&return_value, ".", EXP_CHARS,
		    &generic_floating_point_number))
    {
      make_invalid_floating_point_number (words);
      return (NULL);
    }
  gen_to_words (words, precision, exponent_bits);

  /* Restore the generic_floating_point_number's storage alloc (and
     everything else).  */
  generic_floating_point_number = save_gen_flonum;

  return return_value;
}

/* Turn generic_floating_point_number into a real float/double/extended.  */
int
gen_to_words (words, precision, exponent_bits)
     LITTLENUM_TYPE *words;
     int precision;
     long exponent_bits;
{
  int return_value = 0;

  long exponent_1;
  long exponent_2;
  long exponent_3;
  long exponent_4;
  int exponent_skippage;
  LITTLENUM_TYPE word1;
  LITTLENUM_TYPE *lp;

  if (generic_floating_point_number.low > generic_floating_point_number.leader)
    {
      /* 0.0e0 seen. */
      if (generic_floating_point_number.sign == '+')
	words[0] = 0x0000;
      else
	words[0] = 0x8000;
      memset (&words[1], '\0', sizeof (LITTLENUM_TYPE) * (precision - 1));
      return (return_value);
    }

  /* NaN:  Do the right thing */
  if (generic_floating_point_number.sign == 0)
    {
      if (precision == F_PRECISION)
	{
	  words[0] = 0x7fff;
	  words[1] = 0xffff;
	}
      else
	{
	  words[0] = 0x7fff;
	  words[1] = 0xffff;
	  words[2] = 0xffff;
	  words[3] = 0xffff;
	}
      return return_value;
    }
  else if (generic_floating_point_number.sign == 'P')
    {
      /* +INF:  Do the right thing */
      if (precision == F_PRECISION)
	{
	  words[0] = 0x7f80;
	  words[1] = 0;
	}
      else
	{
	  words[0] = 0x7ff0;
	  words[1] = 0;
	  words[2] = 0;
	  words[3] = 0;
	}
      return (return_value);
    }
  else if (generic_floating_point_number.sign == 'N')
    {
      /* Negative INF */
      if (precision == F_PRECISION)
	{
	  words[0] = 0xff80;
	  words[1] = 0x0;
	}
      else
	{
	  words[0] = 0xfff0;
	  words[1] = 0x0;
	  words[2] = 0x0;
	  words[3] = 0x0;
	}
      return (return_value);
    }
  /*
   * The floating point formats we support have:
   * Bit 15 is sign bit.
   * Bits 14:n are excess-whatever exponent.
   * Bits n-1:0 (if any) are most significant bits of fraction.
   * Bits 15:0 of the next word(s) are the next most significant bits.
   *
   * So we need: number of bits of exponent, number of bits of
   * mantissa.
   */
  bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
  littlenum_pointer = generic_floating_point_number.leader;
  littlenums_left = (1
		     + generic_floating_point_number.leader
		     - generic_floating_point_number.low);
  /* Seek (and forget) 1st significant bit */
  for (exponent_skippage = 0; !next_bits (1); ++exponent_skippage);;
  exponent_1 = (generic_floating_point_number.exponent
		+ generic_floating_point_number.leader
		+ 1
		- generic_floating_point_number.low);
  /* Radix LITTLENUM_RADIX, point just higher than
     generic_floating_point_number.leader. */
  exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
  /* Radix 2. */
  exponent_3 = exponent_2 - exponent_skippage;
  /* Forget leading zeros, forget 1st bit. */
  exponent_4 = exponent_3 + ((1 << (exponent_bits - 1)) - 2);
  /* Offset exponent. */

  lp = words;

  /* Word 1. Sign, exponent and perhaps high bits. */
  word1 = ((generic_floating_point_number.sign == '+')
	   ? 0
	   : (1 << (LITTLENUM_NUMBER_OF_BITS - 1)));

  /* Assume 2's complement integers. */
  if (exponent_4 < 1 && exponent_4 >= -62)
    {
      int prec_bits;
      int num_bits;

      unget_bits (1);
      num_bits = -exponent_4;
      prec_bits = LITTLENUM_NUMBER_OF_BITS * precision - (exponent_bits + 1 + num_bits);
      if (precision == X_PRECISION && exponent_bits == 15)
	prec_bits -= LITTLENUM_NUMBER_OF_BITS + 1;

      if (num_bits >= LITTLENUM_NUMBER_OF_BITS - exponent_bits)
	{
	  /* Bigger than one littlenum */
	  num_bits -= (LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits;
	  *lp++ = word1;
	  if (num_bits + exponent_bits + 1 >= precision * LITTLENUM_NUMBER_OF_BITS)
	    {
	      /* Exponent overflow */
	      make_invalid_floating_point_number (words);
	      return (return_value);
	    }
	  if (precision == X_PRECISION && exponent_bits == 15)
	    {
	      *lp++ = 0;
	      *lp++ = 0;
	      num_bits -= LITTLENUM_NUMBER_OF_BITS - 1;
	    }
	  while (num_bits >= LITTLENUM_NUMBER_OF_BITS)
	    {
	      num_bits -= LITTLENUM_NUMBER_OF_BITS;
	      *lp++ = 0;
	    }
	  if (num_bits)
	    *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS - (num_bits));
	}
      else
	{
	  if (precision == X_PRECISION && exponent_bits == 15)
	    {
	      *lp++ = word1;
	      *lp++ = 0;
	      if (num_bits == LITTLENUM_NUMBER_OF_BITS)
		{
		  *lp++ = 0;
		  *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS - 1);
		}
	      else if (num_bits == LITTLENUM_NUMBER_OF_BITS - 1)
		*lp++ = 0;
	      else
		*lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS - 1 - num_bits);
	      num_bits = 0;
	    }
	  else
	    {
	      word1 |= next_bits ((LITTLENUM_NUMBER_OF_BITS - 1) - (exponent_bits + num_bits));
	      *lp++ = word1;
	    }
	}
      while (lp < words + precision)
	*lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS);

      /* Round the mantissa up, but don't change the number */
      if (next_bits (1))
	{
	  --lp;
	  if (prec_bits > LITTLENUM_NUMBER_OF_BITS)
	    {
	      int n = 0;
	      int tmp_bits;

	      n = 0;
	      tmp_bits = prec_bits;
	      while (tmp_bits > LITTLENUM_NUMBER_OF_BITS)
		{
		  if (lp[n] != (LITTLENUM_TYPE) - 1)
		    break;
		  --n;
		  tmp_bits -= LITTLENUM_NUMBER_OF_BITS;
		}
	      if (tmp_bits > LITTLENUM_NUMBER_OF_BITS || (lp[n] & mask[tmp_bits]) != mask[tmp_bits])
		{
		  unsigned long carry;

		  for (carry = 1; carry && (lp >= words); lp--)
		    {
		      carry = *lp + carry;
		      *lp = carry;
		      carry >>= LITTLENUM_NUMBER_OF_BITS;
		    }
		}
	    }
	  else if ((*lp & mask[prec_bits]) != mask[prec_bits])
	    lp++;
	}

      return return_value;
    }
  else if (exponent_4 & ~mask[exponent_bits])
    {
      /*
       * Exponent overflow. Lose immediately.
       */

      /*
       * We leave return_value alone: admit we read the
       * number, but return a floating exception
       * because we can't encode the number.
       */
      make_invalid_floating_point_number (words);
      return return_value;
    }
  else
    {
      word1 |= (exponent_4 << ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits))
	| next_bits ((LITTLENUM_NUMBER_OF_BITS - 1) - exponent_bits);
    }

  *lp++ = word1;

  /* X_PRECISION is special: it has 16 bits of zero in the middle,
     followed by a 1 bit. */
  if (exponent_bits == 15 && precision == X_PRECISION)
    {
      *lp++ = 0;
      *lp++ = 1 << (LITTLENUM_NUMBER_OF_BITS) | next_bits (LITTLENUM_NUMBER_OF_BITS - 1);
    }

  /* The rest of the words are just mantissa bits. */
  while (lp < words + precision)
    *lp++ = next_bits (LITTLENUM_NUMBER_OF_BITS);

  if (next_bits (1))
    {
      unsigned long carry;
      /*
       * Since the NEXT bit is a 1, round UP the mantissa.
       * The cunning design of these hidden-1 floats permits
       * us to let the mantissa overflow into the exponent, and
       * it 'does the right thing'. However, we lose if the
       * highest-order bit of the lowest-order word flips.
       * Is that clear?
       */

      /* #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)
	 Please allow at least 1 more bit in carry than is in a LITTLENUM.
	 We need that extra bit to hold a carry during a LITTLENUM carry
	 propagation. Another extra bit (kept 0) will assure us that we
	 don't get a sticky sign bit after shifting right, and that
	 permits us to propagate the carry without any masking of bits.
	 #endif */
      for (carry = 1, lp--; carry && (lp >= words); lp--)
	{
	  carry = *lp + carry;
	  *lp = carry;
	  carry >>= LITTLENUM_NUMBER_OF_BITS;
	}
      if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
	{
	  /* We leave return_value alone: admit we read the
	   * number, but return a floating exception
	   * because we can't encode the number.
	   */
	  *words &= ~(1 << (LITTLENUM_NUMBER_OF_BITS - 1));
	  /* make_invalid_floating_point_number (words); */
	  /* return return_value; */
	}
    }
  return (return_value);
}

#if 0 /* unused */
/* This routine is a real kludge.  Someone really should do it better,
   but I'm too lazy, and I don't understand this stuff all too well
   anyway. (JF)  */
static void
int_to_gen (x)
     long x;
{
  char buf[20];
  char *bufp;

  sprintf (buf, "%ld", x);
  bufp = &buf[0];
  if (atof_generic (&bufp, ".", EXP_CHARS, &generic_floating_point_number))
    as_bad ("Error converting number to floating point (Exponent overflow?)");
}
#endif

#ifdef TEST
char *
print_gen (gen)
     FLONUM_TYPE *gen;
{
  FLONUM_TYPE f;
  LITTLENUM_TYPE arr[10];
  double dv;
  float fv;
  static char sbuf[40];

  if (gen)
    {
      f = generic_floating_point_number;
      generic_floating_point_number = *gen;
    }
  gen_to_words (&arr[0], 4, 11);
  memcpy (&dv, &arr[0], sizeof (double));
  sprintf (sbuf, "%x %x %x %x %.14G   ", arr[0], arr[1], arr[2], arr[3], dv);
  gen_to_words (&arr[0], 2, 8);
  memcpy (&fv, &arr[0], sizeof (float));
  sprintf (sbuf + strlen (sbuf), "%x %x %.12g\n", arr[0], arr[1], fv);

  if (gen)
    {
      generic_floating_point_number = f;
    }

  return (sbuf);
}

#endif

/* end of atof-ieee.c */
